Clock jitter or phase noise is a very common and important specification for many applications. Phase-locked loops (PLLs) are commonly employed to reduce clock jitter. However, the reference spur in a phase locked loop can result in a large jitter. Many techniques have been proposed to reduce reference spur in PLL, like reducing the gain (Kvco) of the voltage-control oscillator (VCO), or using a higher order filter to reduce VCO control voltage ripple. Previous works have demonstrated that the reference spur level is controlled as low as −65 dBc using third-order loop filter. One recent work controls the reference spur below −74 dBc through reducing Kvco. With previous techniques the PLL architecture is complicated and the added extra PLL blocks may burn more power or introduce new noise sources.